In general, a main transmitter and a repeater are installed according to an environmental geography and topography and a service coverage area. The repeater is installed in an area where a signal from a main transmitter is received at a weak level, and it can solve an unstable reception and expand a coverage area of the main transmitter.
FIG. 1 is a view for explaining an example of a service through conventional repeaters using different frequencies.
Referring to FIG. 1, in the service using the conventional repeaters, a main transmitter 101 transmits a signal at a transmission frequency A, and repeaters 102 to 105 respectively re-transmit the signal at frequencies B, C, D and E that are different from the transmission frequency A. The repeaters 102 to 105 of FIG. 1 use different frequencies B, C, D and E to prevent unstable reception of the signal from the main transmitter 101 and expand the service coverage area. Since the repeaters 102 to 105 use multiple frequency bands, a large amount of frequency resources are consumed, thus degrading frequency use efficiency.
If multiple repeaters provide a broadcasting service using the same frequency as that of the main transmitter, the frequency can be reused even over a short distance, thus improving the frequency use efficiency.
FIG. 2 is a view for explaining another example of a service using conventional repeaters. In FIG. 2, the repeaters are on-channel repeaters using the same frequency.
That is, a main transmitter 201 transmits a signal at a transmission frequency A, and on-channel repeaters 202 to 205 re-transmit the signal at the same frequency as the transmission frequency A. However, since a high isolation of Tx/Rx antenna is required, the service using the on-channel repeaters has limitations of low utilization of existing transmission facilities and high investment costs.
A distributed transmission network may be implemented using distributed translators (DT×R). This distributed transmission method has advantages of maximized use of the existing transmission facilities, short implementation time, cost efficiency, and improved frequency use efficiency.
FIG. 3 is a view for explaining an example of a service using distributed translators. A main transmitter 301 transmits a broadcasting signal at a transmission frequency A, and distributed translators 302 to 305 re-transmit the signal at a frequency B different from the transmission frequency A.
If a network is configured using a technology associated with the on-channel repeaters or distributed translators, the frequency is reused, thereby improving the frequency use efficiency. However, interference with adjacent repeaters occurs because a single frequency is used among multiple transmitters or repeaters. To mitigate the interference among multiple transmitters or repeaters, an identification signal having an excellent correlation characteristic is assigned to each transmitter and repeater and is inserted in a signal to be transmitted. By using a signal analyzer, a desired identification signal can be detected in order to display channel profiles including interferences from other signals.
A number of sequences used as the identification signal are embedded in a spread spectrum form in order to minimize an influence of a conventional DTV service. For this reason, a high bit resolution is required for signal representation. Also, a long sequence is used as an identification signal to acquire an excellent correlation characteristic. For example, in the Advanced Television Systems Committee digital TV (ATSC DTV) system, a Kasami sequence having a specific length is used, and inserted with signal power smaller than signal power of the DTV signal by from 21 dB to 39 dB. Thus, a large computation amount, i.e., high complexity is undesirably needed for implementation of a signal analyzer, i.e., an identification signal analyzing apparatus that detects and analyzes such an identification signal.
Therefore, there has been proposed a technology associated with identification signal analysis using a partial correlation having low complexity to analyze identification signals having a high bit resolution and a long length.
However, the technology associated with the identification signal analysis has limitations in which the power of detected identification signal can be attenuated and separated, which results in attenuation and separation of a channel profile.